sdturner:
Yes, You can feed 9V to the board and you can use the 5V supply generated by the Arduino so long as the total current is less than 500mA.
No. The Mini is based on the LP2985 which has a maximum output of 150mA, not 500.
FYI, A SD Card can draw 65-75mA when reading or writing:
http://www.flashgenie.net/img/productmanualsdcardv2.2final.pdf